Oil shale, tar sands, oil sands and subsurface media in specific areas contain useful hydrocarbons. For example, it has been reported that there are vast oil shale deposits in the United States, and in particular, in the States of Colorado, Utah and Wyoming; with over 1.5 trillion barrels of oil in the oil shale in these States. There have been many attempts to extract the hydrocarbons from these subsurface deposits.
Some of these applications involve removal of the subsurface media to above ground and the use of a retort to remove the oil. To avoid the step of excavating or mining, a number of in-situ processes have been proposed.
One such proposal employs relatively low microwave power supplied by a magnetron. The down hole microwave generator is disclosed in U.S. Pat. No. 4,193,448 issued Mar. 18, 1980 to Calhoun G. Jeambey, as inventor, and the use of this generator is disclosed in detail in U.S. Pat. No. 4,817,711 issued Apr. 4, 1989 to Calhoun G. Jeambey as inventor. The microwave generator is a mixer apparatus similar to those used in microwave ovens and is relatively ineffective for controlled heating and removing of hydrocarbons. The apparatus heats the easily reached hydrocarbons in the pores of the rock and will leave much of the hydrocarbon away from the bore hole untouched.
Although not designed for commercially recovering hydrocarbons from oil shale or other subterranean locations, a high power microwave system is disclosed in U.S. Pat. No. 5,299,887 issued Apr. 5, 1994 to Donald L. Ensley, one of the inventors herein. This system is disclosed for the removal of contaminant from a sub-surface soil matrix. It is taught in this patent that the application of high power microwave energy to chlorinated hydrocarbons contaminated (CHC) soil causes micro-fractionation of various soil aggregates, including clay and rock formations. This effect increases the local permeability and resulting diffusion rates for egress of both liquid and vapor phase CHC.
The teachings of the Ensley U.S. Pat. No. 5,299,887 patent were included in U.S. Pat. No. 6,012,520 by Andrew Yu and Peter Tsou as an alternative to use of high-pressure water jet drilling to create a high-permeability web in a hydrocarbon reservoir.